Few linguistic terms in the history of anthropology have had greater currency than mana. While anthropological debate about this term has tended to center on the correct interpretation of the native concept, little attention has been given to the etymology of the word. When this is pursued, a novel perspective on this pivotal concept emerges. Cognates meaning 'thunder'and 'wind' suggest that Proto-Oceanic *mana did not refer to a detachable spiritual or supernatural power that could be possessed by humans, but rather to powerful forces of nature such as thunder and storm winds that were conceived as the expression of an unseen supernatural agency. As Oceanic-speaking peoples spread eastward, the notion of an unseen supernatural agency became detached from the physical forces of nature that had inspired it and assumed a life of its own. It is argued that the process that gave rise to the canonical sense of mana, as this is commonly understood in the anthropology of religion, is part of a larger process in which widespread and apparently arbitrary features of human cultures were inspired by a prescientific attempt to understand the forces of nature.